Conventionally, there is known, as a refrigeration cycle apparatus including an expander, a refrigeration cycle apparatus including a compression mechanism which connects an auxiliary compression mechanism and an expansion mechanism by one shaft and compresses a refrigerant, the auxiliary compression mechanism for further compressing the refrigerant discharged from the compression mechanism, a radiator for cooling the refrigerant discharged from the auxiliary compression mechanism, an evaporator for heating the refrigerant flowing out from the expansion mechanism, a bypass flow passage bypassing the expansion mechanism, a bypass valve installed in the bypass flow passage, and an operating device for controlling the operation of the bypass valve, in which the operating device changes the degree of opening of the bypass valve to adjust a high-pressure side pressure (see, for example, Patent Document 1).
The above-mentioned refrigeration cycle apparatus provides high power recovery effect over a wide operating range even when it is difficult for the used expander to adjust the high-pressure side pressure to an optimal value due to a constraint of a constant density ratio.
Here, the density ratio refers to a ratio of a density (DE) of the refrigerant flowing in the expansion mechanism and a density (DC) of the refrigerant flowing in the auxiliary compression mechanism (DE/DC).
Patent Document 1: JP 3708536 B1